Preparation Of Carbon-based Composite Materials And Research Of Their Catalytic Degradation Performance Of Organic Pollutants In Water

The rapid development of today’s society not only brings people increasingly convenient living conditions,but also brings a lot of environmental problems.Water pollution is the most prominent one.Catalytic technology is a very efficient and feasible way for the treatment of water pollution.Researchers have made great contributions in the field of environmental catalysis and achieved gratifying results,but there are still problems to be optimized in the research and development of catalysts.We have summarized the following problems:the deposition of heterojunction,which causes small specific surface area;low visible light utilization rate of photocatalysts;most of the catalysts lack the function of indicating the reaction process.In recent years,carbon materials have been widely used in catalytic fields.Carbon material is a porous carbonaceous material and often used as the carrier of catalysts because of its high specific surface area,high conductivity and stable electrochemical properties.Carbon material plays a good role in optimizing catalyst and has advantages in environmental catalysis.Our work is to design and prepare carbon based composite catalysts to improve the performance of catalysts and provide more effective ways for the degradation of pollutants in water.1.The carbon material is a common support material that fixes the semiconductor photocatalyst nanoparticles.Because it has a large surface area,the nanoparticles can be distributed and fixed in its surface,and the defective site of the surface and the oxygen-containing group can provide a rich nucleation site for uniform growing and anchoring of nanoparticles.Therefore,CuO/WO₃/Cu@CN catalyst was prepared by compositing Cu（salen）PW₁₂ complex precursor with GO via solvothermal method.The specific surface area of CuO/WO₃/Cu@CN is up to 490.61 m² g^-1.The CuO/WO₃/Cu@CN catalyst can effectively catalyze the reaction of 4-NP reducing to 4-AP,and had good cycle stability.CuO/WO₃/Cu@CN can effectively promote the separation of photo-generated e^-and h⁺and inhibit their recombination,and effectively degrade organic dyes under UV-vis light irradiation.The photocatalytic mechanism was derived,and·OH was considered to be the main active species,and hydrogen was produced during photocatalytic process.Photocatalytic decomposition water producing hydrogen experiment and free radical capturing experiment further confirmed the correctness of the mechanism.The enhanced performance of CuO/WO₃/Cu@CN is attributed to:GO as a carrier of the catalyst can effectively increase the specific surface area and solve the problem of heterogeneous pulverization;as a precursor,Cu（salen）-PW₁₂ complex can not only provide all elements forming heterojunction,but also be inserted between GO layers as a"support column"to prevent the stacking of GO layers during reaction and calcination process.At the same time,in the solvothermal reaction process,PW₁₂ acts as a catalyst to reduce GO to r GO,which improves the conductivity of the material;the formation of N-doped graphene in the calcination process increases the performance of catalytic,so that CuO/WO₃/Cu@CN satisfy the potential of hydrogen production.2.Porphyrin has a high extinction coefficient in the visible region,so it can capture effective light in nature and convert light energy into electric energy.Moreover,the combination of porphyrin and graphene can form a charge donor-receptor（D-A）system with good energy conversion mechanism,which can accelerate the transfer of photogenerated carriers and improve the photocatalytic performance.Porphyrin coordinates with metal forming metal-porphyrin,which can increase the stability of porphyrin,and the presence of the center metal facilitates the flow of electrons.Therefore,we combined metal porphyrin-functionalized FLIG with porous WO₃,and prepared an efficient Z-scheme FLIG/WO₃ photocatalyst（LIG=laser-induced graphene）.The visible light absorption range of0.4FLIG/WO₃ reaches from 518 nm to 768 nm.Under visible light,photocatalytic degradation experiments of cyclopropoxicle（CIP）show that the photocatalytic property of0.4FLIG/WO₃ is 2.8 and 8.0 times higher than pure FLIG and porous WO₃,respectively.The bonding of the porphyrin group and the construction of Z-scheme heterojunction result in a significant increase in photocatalytic performance.The porphyrin group enhanced the ability to absorb visible light,while Z-scheme effectively increased the separation efficiency of the photo-generated carrier.Through mass spectrometry analysis of the intermediate product of the CIP degradation process,a reasonable degradation path is proposed.Free radical capture experiment,band-energy structure analysis and ESR technology show that·OH and·O₂^-are active substances in the photo-catalysis.3.The lanthanide complex is considered to be a potential luminescent material for detecting nitrophenol compound（NPC）.And rare earth elements have 4f empty orbitals,so they have certain catalytic activity.However,most rare earth complexes have poor conductivity,but their conductivity can be improved by compounding with carbon materials.In this work,we wrapped the CTAB modified carbon sphere（CS）with Eu-L complex prepared CS@Eu-L catalyst.CS@Eu-L can realize fluorescence sensing,in situ removing and real-time monitoring of NPC.CS@Eu-L can detect 4-NP in aqueous solution(K_sv=4.1×10⁴M^-1).At the same time,CS@Eu-L can also be used as a catalyst for reduction 4-NP,and the apparent reaction rate is 5.92×10^-3 s^-1.The mechanism of selective detection of NPC can be explained by energy competition between NPC and Eu（III）.The enhanced catalytic activity of CS@Eu-L is due to the fact that carbon spheres provide a good electron transfer channel for the reaction.In addition,the fluorescence detection and catalytic performance of CS@Eu-L have good cycle stability,and the fluorescence emission of CS@Eu-L can reflect the degradation degree of NPC in the reaction process.The choice of ligands was discussed.In addition,DAP small molecule rare earth complexes were also constructed.It was found that they did not have the fluorescence detection and catalytic reduction performance of NPC.Therefore,it is concluded that the rare earth complexes of organic biphenyl carboxylic acid and benzocarboxylic acid ligands are more suitable for the fluorescence detection and catalytic reduction of NPC.